Cytotoxicity And Genetic Toxicology Of 1-Chloro-3-Butene-2-ol And 1-Chloro-3-Buten-2-one

1,3-Butadiene (BD) is an important industrial chemical used in the synthesis ofrubber and plastic. The major environmental source of the carcinogenic air pollutantis the incomplete combustion of fossil fuels and biomass. The carcinogenicity of BDstems from its in vivo metabolites rather than BD itself. BD has two metabolicpathways. In one of the two pathways, BD is metabolized to epoxides, such as3,4-epoxy-1-butene and1,2,3,4-diepoxybutane. In the other pathway, BD isbiotransformed to1-chloro-2-hydroxy-3-butene (CHB), which may be furtherbioactivated to1-chloro-3-buten-2-one (CBO). Recently, it was showed that CBOcould react with2′-deoxyadenosine and2′-deoxycytidine and cause globin cross-linking in erythrocytes, suggesting that CBO had the potential to damage DNA andproteins. However, it has not been investigated whether CHB and CBO havecytotoxicity and genotoxicity.In the present study, we investigated the cytotoxicity and genotoxicity of CHBand CBO in human normal hepatocyte L02cells using the MTT assay, the relativecloning effciency, the comet assay, the detection of mitochondrial membranepotential, and HPLC.The results provided clear evidence for CHB and CBO being both cytotoxic andgenotoxic with CBO being approximately100-fold more potent than CHB. In L02cells, CHB generated both single-strand breaks and alkali-labile sites (ALS), whereasCBO produced only ALS. Both CHB and CBO did not induce DNA-DNA cross-links.CHB did not directly result in DNA breaks,whereas CBO was capable of directlygenerating breaks on DNA.Further investigations showed that CHB could be hydrolyzed to othercompounds that had genotoxicity and the chlorine atom probably played a key role inthe genotoxicity of CHB. CBO could cause DNA damage by direct reaction withDNA, but the possibility that CBO induced oxidative stress, which caused DNA damage, could not be excluded. In addition, CBO-mono-GSH and CBO-di-GSH, thereaction products of CBO and glutathione (GSH), were found to be genotoxic as well,but their genotoxicity was much weaker than that of CBO. The genotoxcity of CBO-mono-GSH was stronger than CBO-di-GSH. These results suggested that CHB andCBO may play an important role in the carcinogenicity of1,3-butadiene.